A virus has been grabbing headlines in the west coast the past several weeks and it one that is usually not on anyone's lists anymore: hepatitis A. Hepatitis A outbreaks in San Diego, Santa Cruz, and Los Angeles have garnered a lot of attention and public health authorities are stepping up measures to contain the fecal-oral spreading virus with emergencies declared in Los Angeles and San Diego. There is also concern of another outbreak in Utah.

Like I discuss in this video and this podcast, hepatitis A was a near ubiquitous virus that everyone contracted during childhood, sometimes with no to minimal symptoms. Others might experience nausea, vomiting, abdominal pain, and jaundice. However, unlike other viral hepatitis viruses (hepatitis B, hepatitis C), this virus does not have a chronic phase of infection that confers risks of cirrhosis and liver cancer. The introduction of the vaccine in 1995 and its adoption as a universal childhood vaccine in the US has dramatically reduced its incidence. However, there are segments of the population that are not vaccinated and were not naturally infected who remain susceptible. Of those susceptible, those with preexisting liver disease because of alcohol, hepatitis C (20% of those tested in the San Diego outbreak), and/or hepatitis B are particularly at risk for having a fulminant infection with hepatitis A. At least 16 people have died during the San Diego outbreak.

Because hepatitis A spreads through the fecal-oral route and has a 28 day incubation period it can cause large outbreaks -- the largest one occurred in 2003 in the Pittsburgh area and was linked to the now defunct Chi Chi's restaurant chain.

I would suspect that it is no accident that the San Diego outbreak has its epicenters within homeless populations. Homeless populations will, by definition, have less access to sanitary facilities for bodily functions as well as for handwashing. They also are likely of an age that did not have the ability to be vaccinated against the virus as children. Additionally, they often cluster together in shelters, encampments, or in enclaves within a city, allowing more opportunity for viral exchange. Medical interventions are also much more difficult to implement with populations that are transitory, mobile, and otherwise hard to reach.

Vaccination, immunoglobulin and sanitation are the two most important tools to end these outbreaks. The US had just 1234 cases of hepatitis A in 2014 -- a 95% decline from the pre-vaccine era -- so it is clear that humans have the capacity to put this virus down. Aggressive case finding coupled with vaccination, immunoglobulin use, and infection control -- all of which are occurring now -- to prevent further spread are what will ultimately prevail.